1. Field of the Invention
The present invention is generally concerned with clutch cover assemblies, that is to say the assembly of parts which, in order to make up a clutch, in particular for an automotive vehicle, is fastened as a unit to a reaction plate or flywheel with a friction disk disposed between them.
2. Description of the Prior Art
As is known, a clutch cover assembly generally comprises a first generally annular member called the cover through which it is adapted to be attached to the associated reaction plate, a second generally annular member called the pressure plate which is constrained to rotate with said cover whilst being mounted so as to be movable axially relative to the latter, and which is adapted to clamp the friction disk axially against the reaction plate, and elastic means which, for the purposes of this clamping or engagement, urge said pressure plate in the direction towards said reaction plate, said elastic means bearing for this purpose on the cover so as to exert a force in the axial direction on the pressure plate.
Elastic means of this kind may, for example, form part of a third generally annular member called the diaphragm spring which is inserted axially between the pressure plate and the cover and comprises, on the one hand, a circumferentially continuous peripheral part forming a Belleville washer and constituting said elastic means and, on the other hand, a central part divided into radial fingers by slots, said central part forming levers by means of which the assembly may be operated to disengage it.
Generally speaking, a diaphragm spring of this kind usually bears directly on the pressure plate having for this purpose an annular bead projecting in the axial direction, possibly subdivided circumferentially into separate bosses.
Be this as it may, in service the internal volume of a clutch cover assembly of this kind is inevitably subjected to an increase in temperature, in particular due to friction forces which are developed between the friction disk on the one hand and, on the other hand, the pressure and reaction plates, each time the clutch is disengaged and each time it is engaged.
In U.S. patent application Ser. No. 601,251 filed Apr. 17, 1984 and now U.S. Pat. No. 4,529,074 there is described a clutch cover assembly pressure plate, suitable for automotive vehicles, of the kind comprising axially projecting cooling fins on the side opposite that which is adapted to operate on a friction disk and certain at least of which are relatively longer cooling fins which extend substantially from its inside perimeter to its outside perimeter, and delimit between them air circulation grooves which are oblique to a radial plane passing through their median area, a distinct and separate confinement member adapted to close off said air circulation grooves in the axial direction over at least part of their length and on the side opposite the pressure plate and fixing means whereby said confinement member is rigidly attached to said pressure plate.
A confinement member of this kind advantageously defines with the air circulation grooves true channels within which, by virtue of the resulting confinement, the circulation of air is forced, that is to say accelerated, which is of positive benefit with regard to the required ventilation.
The cooling fins take up warm air at the inside perimeter of the pressure plate, within the axial volume of the assembly, and direct it to the outside perimeter of the pressure plate, by means of the air circulation channels delimited between them and the confinement member, and so evacuate it.
This arrangement calls for two remarks: firstly it may be desirable to eliminate the cooling fins; secondly, and whatever else might apply, it may also be desirable to further improve the cooling effect.